8(7-x)(x+4)=0

Solution for 8(7-x)(x+4)=0 equation:

8(7-x)(x+4)=0

We add all the numbers together, and all the variables

8(-1x+7)(x+4)=0

We multiply parentheses ..

8(-1x^2-4x+7x+28)=0

We multiply parentheses

-8x^2-32x+56x+224=0

We add all the numbers together, and all the variables

-8x^2+24x+224=0

a = -8; b = 24; c = +224;
Δ = b2-4ac
Δ = 242-4·(-8)·224
Δ = 7744
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{7744}=88$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(24)-88}{2*-8}=\frac{-112}{-16}
=+7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(24)+88}{2*-8}=\frac{64}{-16}
=-4
$